DESCRIPTION: (Adapted from the application) The long term goal of this research is to develop methods and instrumentation to obtain improved quantification of the radioisotope distribution in humans and animals. SPRINT II is a third generation SPECT instrument developed as part of this ongoing effort. The focus of this proposal is to define and validate methods of data acquisition, correction, and analysis of SPECT data which will facilitate clinical and experimental use of this instrument and exploit some of its unique features. The applicants will investigate two innovative data acquisition strategies with SPRINT II, which should measurably increase data accuracy and improve signal-to-noise ratios: 1) determine the value of acquiring a vertex view of the brain during a conventional SPECT acquisition and incorporating this information into the image reconstruction or parameter estimation process; 2) determine the optimal aperture resolution to best estimate myocardial rate constants for freely diffusible tracers such as SQ30217. The analysis will include noninvasive determination of the input function, the effects of gating, and temporal variation of the slit width. The applicants will also develop and evaluate methods to measure and correct for scatter, attenuation, and patient motion and make hardware improvements to SPRINT II for the purpose of improving both spatial and energy resolution.